Gold nanodome SERS platform for label-free detection of protease activity

Abstract

Surface-enhanced Raman scattering provides a promising technology for sensitive and selective detection of protease activity by monitoring peptide cleavage. Not only are peptides and plasmonic hotspots similarly sized, Raman fingerprints also hold large potential for spectral multiplexing. Here, we use a gold-nanodome platform for real-time detection of trypsin activity on a CALNNYGGGGVRGNF substrate peptide. First, we investigate the spectral changes upon cleavage through the SERS signal of liquid-chromatography separated products. Next, we show that similar patterns are detected upon digesting surface-bound peptides. We demonstrate that the relative intensity of the fingerprints from aromatic amino acids before and after the cleavage site provides a robust figure of merit for the turnover rate. The presented method offers a generic approach for measuring protease activity, which is illustrated by developing an analogous substrate for endoproteinase Glu-C.

Polycaprolactone-Based, Porous CaCO3 and Ag Nanoparticle Modified Scaffolds as a SERS Platform With Molecule-Specific Adsorption

“…Their modification, for example, by inorganic nanoparticles leading to the socalled hybrid (Saveleva et al, 2019) structures or scaffolds makes them a unique platform, where the porosity and the concentration or the filling factor of the metal nanoparticles can be controlled. Furthermore, their uniqueness lies in a possibility to adsorb molecules-a property, which has been identified as a very important factor enabling high and stable amplification (Wuytens et al, 2017). This principle, demonstrated in this work for porous materials in combination with their adsorption of molecules, resulted in significant amplification of the surfaceenhanced Raman signals relevant for detection of a wide range of molecules.…”

“…Another aspect that appears to be important in SERS is the attachment of molecules-indeed, attached molecules have been reported to enable both stability and a high level of amplification (Wuytens et al, 2017).…”

Waveguide-based surface-enhanced Raman spectroscopy detection of protease activity using non-natural aromatic amino acids

“…The SERS peak originating from the CN-F is expected to stay constant and can thus serve as a normalization peak. The F and CN-F peak counts are integrated, and the F/CN-F peak intensity ratio is used as a metric for the efficiency of trypsin cleavage [16]. Fig.…”

“…Uncontrolled aggregation of metal nanoparticles can however create reproducibility issues. To overcome these, the peptide can be immobilized on a well-controlled SERS structure and then specifically cleaved by a protease [15,16]. This allows a reproducible, quantitative approach of great interest for protease activity sensing.…”

“…In this work, we used the nanoplasmonic slot waveguide to demonstrate waveguide-based SERS detection of trypsin activity via the cleavage of peptide substrate. The concept of free-space SERS detection of protease activity was previously demonstrated on gold nanodomes for the detection of trypsin activity through the SERS spectra of surface-bound peptides consisting of only natural amino acids [16]. However, due to the poorer SERS performance of the nanoplasmonic slot waveguide compared to free-space gold nanodomes, just the natural aromatic acids do not provide sufficient SERS signal for waveguide-based detection [36].…”